A reactor is a circuit component that increases or reduces a voltage. For example, PTL 1 describes a reactor that is used as a converter mounted in a vehicle such as a hybrid vehicle. The reactor described in PTL 1 includes a magnetic core that has an E-shaped cross section, which is a so-called pot-shaped core. The magnetic core includes a solid-cylindrical internal core portion that is disposed inside a coil, a hollow-cylindrical core portion that is disposed so as to surround the outer periphery of the coil, and a pair of disk-shaped core portions that are disposed on both end surfaces of the coil (PTL 1). In the pot-shaped core, the internal core portion and the hollow-cylindrical core portion, which are concentrically disposed, are coupled to each other by the disk-shaped core portions, and a closed magnetic path is formed. Moreover, PTL 1 discloses that the cross-sectional area of the internal core portion can be reduced by making the saturation magnetic flux density of the internal core portion be higher than those of the hollow-cylindrical core portion and the disk-shaped core portions, and thereby a small reactor can be obtained.